1. Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110015, China.
2. State Key Lab for Rapidly Solidified Non-equilibrium Alloys, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110015, China.
3. Department of Physics and Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.